Foundations of Biology 2 Midterm 3 Chapter 28 1 28 3 Bacteria and Archaea Similarities Differences Unicellular Prokaryotic lack membrane bound nucleus Bacteria have cell walls made of peptidoglycan Archaea have hydrocarbon tails on the phospholipid bilayer of the plasma membrane called isoprene Archaea is more closely related to eukaryotes than to bacteria 28 1 Why Do Biologists Study Bacteria and Archaea Biological Impact o Ancient Prokaryotes were the only life form on Earth at least 1 7 billion years 5000 have been formally named millions still have yet to be discovered 1012 bacterial cells on the skin 1014 bacterial and archaeal cells in stomach and intestines If each individual bacteria archaea cell lined up next to each other it would be longer than the Milky Way o Abundance o Diversity Oxygen free environments Hot springs Salt flats Extreme temperatures All levels of seawater Medical Importance o Some bacteria are pathogenic may cause disease an abnormal condition of an organism which interrupts the normal bodily functions o Koch s Postulates link between a particular species of bacteria and a specific proposed that bacteria is responsible for causing infectious diseases spreading from infected individual to uninfected individual studied anthrax disease in cattle and other grazing animals blood poisoning Microbe must be present in individuals suffering from disease and absent from healthy individuals Organism must be isolated and grown in a pure culture away from the host organism If organisms from pure culture are injected into healthy individual disease symptoms should appear Foundations of Biology 2 Midterm 3 Organism should be isolated from diseased experimental animal grown in a pure culture and the size shape and color should be the same as the original o Germ Theory of Disease Certain diseases are infectious can be passed from person to person Transmission and growth of bacteria and viruses Foundation of modern medicine improving sanitation washing hands Understanding of sanitation sterile procedures medicines penicillin What Makes Some Bacterial Cells Pathogenic decrease in bacterial infections o Virulence ability to cause disease heritable trait that varies among individuals in a population Ex Escherichia coli usually harmless inhabitants of the GI tract in humans and mammals other forms of E coli cause food poisoning o Genome of virulent strains contains genes for proteins that allow the cells to adhere to the host cells and secrete toxins that disrupt host cells o Decrease in sanitation makes spreading infectious disease very easy Antibiotics molecules that kill bacteria o Constant used of antibiotics causes evolution of drug resistance strains of pathogenic bacteria Bioremediation soluble tree of life o Bioremediation Strategies o Most serious pollutants are hydrophobic organic compounds are not water o Compounds become sediments that are ingested by organisms polluting the whole Fertilize contaminated sites to encourage growth of existing bacteria and archaea that degrade toxic compounds Ex Nitrogen was added to synthesize enzymes to increase the growth of bacteria and archaea Adding specific species of bacteria and archaea to contaminated sites Extremophiles bacteria or archaea that live in extreme conditions o First forms of life on earth lived at high temperatures and pressures that lacked o If bacteria archaea can survive in extreme conditions bound to find cells like that oxygen on distant planets o Commercial and industrial usages 28 2 How do Biologists Study Bacteria and Archaea Techniques for Isolating Bacteria and Archaea Enrichment Culture isolate cells that grown in response to specific conditions create an abundant sample of bacteria that thrive under specific conditions o Ex Can bacteria live a mile below Earth s surface bacteria can go through cellular respiration below Earth s surface by using H2 electron donor and Fe3 electron acceptor black magnetic grains Fe3O4 will accumulate and shed as Foundations of Biology 2 Midterm 3 waste product as an indicator of cellular respiration one species grew in the enrichment culture Direct Sequencing documenting the presence of bacteria and archaea that cannot be grown in culture distinct characteristics to represent an independent branch on an evolutionary tree allows researches to identify species that have never been seen o Isolating DNA from samples taken directly from the environment purifying and sequencing specific genes analyzing where DNA sequences are found on the phylogenetic tree of bacteria and archaea 4 Categories of Archaea o Halophiles desire for salt o Sulfate Reducers cells that produce H2S as by product of cellular respiration o Methanogens produce methane gas as by product of cellular respiration o Thermophiles growth in very high temperatures Phylogenies evolutionary relationships among species and lineages how closely or distantly related species are to each other 28 3 What themes occur in the diversification of bacteria and archaea Morphological Diversity o Size measure in micrometers o Shape filaments spheres rods chains or spirals o Motility swimming movements powered by flagella o Cell Wall Composition Gram Positive Gram stains purple retains more stain Large peptidoglycan layer Gram Negative Gram stains pink retains less stain Plasma membrane surrounded by a cell wall thin layers of peptidoglycan and phospholipid bilayer Foundations of Biology 2 Midterm 3 Metabolic Diversity variation in chemical reactions that go on inside these cells Source of C C Bonds Phototroph from sunlight Source of Energy ATP Synthesis Chemoorganotroph from organic molecules sugars Chemolithotroph from inorganic molecules ammonia methane Chemolithoautotroph Photoautotroph Chemorganoautotroph Autotrophs self synthesized from carbon dioxide methane and other simple molecules Heterotrophs synthesized from molecules produced by other organisms Photoheterotroph Chemoorganoheterotroph Chemolithotrophic Heterotroph Cyanobacteria lineage of photosynthetic bacteria first organisms to perform oxygen producing photosynthesis Aerobic Respiration with oxygen Anaerobic Respiration without oxygen Nitrogen Fixation Organisms need nitrogen to synthesize proteins and nucleic acids N2 is abundant in the atmosphere but organisms need to convert that into ammonia NH3 or nitrate NO3 Cyanobacteria that live in surface waters of the ocean are capable of nitrogen fixation Nitrogen fixing bacteria live in close association with
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